Background: There are abnormalities in vitamin D metabolism in people with calcium nephrolithiasis, but limited data are available on vitamin D status in dogs with calcium oxalate (CaOx) urolithiasis. Objective: To compare serum concentrations of vitamin D metabolites in dogs with and without hypercalciuric CaOx urolithiasis. Animals: Thirty-eight dogs with (n = 19) and without (n = 19) a history of CaOx urolithiasis and hypercalciuria. Methods: Retrospective cross-sectional study. Serum 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH) 2 D], and 24,25-dihydroxyvitamin D [24,25(OH) 2 D] were measured. The ratios of 25(OH)D/24,25(OH) 2 D and 1,25(OH) 2 D/25(OH)D were compared between cases and controls. Results: There were no significant differences between cases and controls when comparing 25(OH)D, 24,25(OH) 2 D, 1,25(OH) 2 D, or 1,25(OH) 2 D/25(OH)D. Cases had higher 25(OH)D/24,25(OH) 2 D (median = 1.40, range = 0.98-1.58) compared to controls (median = 1.16, range = 0.92-2.75; P =.01). There was overlap in the ranges for 25(OH)D/24,25(OH) 2 D between cases and controls, but 6 cases (32%) had ratios above the control dog range. There was a moderate positive correlation between the ratio of 25(OH)D/24,25(OH) 2 D and urinary calcium-to-creatinine ratios (r = 0.40, 95% confidence interval = 0.10-0.64; P =.01). Conclusions and Clinical Importance: These data suggest that decreased conversion of 25(OH)D to 24,25(OH) 2 D occurs in a subset of dogs with CaOx urolithiasis. Abnormalities in vitamin D metabolism might contribute to stone risk in dogs.
Bibliographical noteFunding Information:
University of Minnesota protocol 1509-33019A. Stored samples were used for this study; they had been previously collected with approval of the protocol above. This was a retrospective cross-sectional study. The study took place at the University of Minnesota Veterinary Medical Center (UMN VMC). Stored (?80?C) serum samples were available from dogs recruited as cases and controls for genetic and metabolic studies on CaOx urolithiasis between February 2011 and November 2015. The dogs were recruited from the patient population at the UMN VMC and through outreach to primary care veterinary clinics and breeders in Minnesota, Iowa, and Wisconsin. Miniature Schnauzers, Bichon Frise, and Shih Tzus were selected to represent breeds where idiopathic hypercalciuria has been reported in CaOx stone formers.
National Institute of Health, Grant/Award Number: 1K01OD019912-03; University of Minnesota, Grant/Award Number: Small Companion Animal Research Grant
© 2019 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.